Among the conventionally-known self-propelled auger-type snow removal machines are ones in which an engine drives an auger and a blower that blows away snow, gathered by the auger, to around the machine through a shooter. Japanese Patent Application Laid-open Publication No. 2007-056445 (hereinafter referred to as “the relevant prior art document”) discloses such a snow removal machine and particularly a technique for switching between a plurality of engine control modes.
The snow removal machine disclosed in the relevant prior art document is constructed in such a manner that a desired one of a plurality of snow removal modes (control modes) is selected via a mode setting switch and that rotation control of the engine is performed in the selected snow removal mode (control mode). In the selected snow removal mode, the engine can be controlled in accordance with a traveling speed corresponding to an operated amount of a travel seed lever.
In each of the control modes, it may sometimes be preferable, in order to achieve detailed snow removal work, that control of a snow removal work section, comprising the auger and the blower, be separated from a traveling speed of the snow removal machine so that a human operator can adjust the traveling speed in accordance with snow removal conditions. In such a case, the human operator can operate the engine in an optimal operating state if the human operator can know, during execution of each of the control modes, whether a current operating state of the engine is in an optimal operating range. In this way, optimal snow removal performance of the machine can be achieved.
In order to know whether the current operating state of the engine is in the optimal operating range, it is conceivable to provide an engine rotation meter. However, with mere provision of such an engine rotation meter, the human operator requires considerable experience or skill in order to judge whether the current operating state of the engine is optimal in the individual control modes.
Besides, if the engine is of a type provided with en electronic governor, a throttle is kept closed while the engine is in a no-load state even when the number of rotations of the engine is maximum (upper limit). Thus, in this case, whether the engine is in the optimal operating state can be known via the engine rotation meter only by the human operator first operating the engine, prior to snow removal work, so that the number of rotations of the engine reaches the maximum and then placing a load on the engine so that the number of rotations of the engine decreases.